Introduction: Electrotherapy Flashcards
may be defined as that which occupies
space & comprises a great number of different
materials.
matter
the smallest particle of an element that
can take part in a chemical reaction
Atom
particle c very small mass, < 10-13
cm diameter; (+) electric charge
Proton
same mass as proton; no charg
Neutron
1/1850 of proton; (-) charge
Electron
the smallest particle of any
substance, element or compound that can
exist alone
Molecule
a basic substance which cannot
be split into simpler substances (ex. Na, Cl)
Elements
a substance formed by the
union of 2 or more elements (ex. NaCl)
Compound
a contact for the induction or
detection of electric activity
ELECTRODE
medium for conducting an electric current
from the body to physiologic monitoring;
ELECTRODE
plate that receives excess
electrons from the negative pole of the
source of current
Cathode
plate that develops a deficiency of
electrons being connected to positive pole
Anode
process in which electric
energy causes a chemical change in a
conducting medium; usually a solution or a
molten substance; means breaking down by
electricity
ELECTROLYSIS
an atom or group of atoms bearing a
(-) or (+) electric charge
IONS
a positively charge ion that in
solution is attracted to (-) electrode
(cathode)
Cations
a negatively charged ion that is
attracted to (+) electrode (anode) in
electrolysis.
Anion
a substance which
contains ions; an element or compound
that when melted or dissolved in water or
other solvent, dissociates into ions & is
able to conduct an electric current
ELECTROLYTES
a non-conducting substance
that offers a barrier to the passage of heat
or electricity
INSULATORS
any substance through
which electrons flow easily; materials
which readily permit the movement of
electrons
CONDUCTORS
EMF
ELECTROMOTIVE FORCE
produced by chemical action in
a cell; the cell consists of 2 dissimilar
metals immersed in an electrolyte & the
principle underlying its action is the
behavior of a metal immersed in a
solution (electrolysis)
EMF
DIFFERENT METHODS OF
PRODUCTION OF ELECTRICITY
- Charging by friction
- Chemical action- in cells
- Electromagnetic Induction- in dynamo
simplest way of producing a static electric
charge is by friction between two dissimilar
materials
Charging by friction
in dynamo
Electromagnetic Induction
used for the production of an EMF
by electromagnetic induction; a collecting
device used to convey the current from the
moving coil of wire to the external circuit;
Dynamo
it is used for all
large scale production of electricity,
including for the main supply
Dynamo
EMI
ELECTROMAGNETIC INDUCTION
The production of an EMF in a conductor
by interaction bet. The conductor and
magnetic lines of force
ELECTROMAGNETIC INDUCTION
PRODUCTION OF EMF IN EMI
- Essentials for EMI are
- Conductor
- Magnetic lines of force
- Movement of one of these relative to the
others
is the production of electrical properties
in one object, which must be a conductor of
electricity by the magnetic lines of force
surrounding another object; the two object do not come in contact with each other, but it is
necessary for to move relative to the other as
it only when magnetic lines of force cut across
the conduction or vice versa that the EMF is
produced
EMI
connected to
milliameter Bar Magnet (provides the
magnetic lines of force
- Coil of wire (conductor)
thermocouple
HEAT
- in a photoelectric celL
- the energy emitted by electromagnetic
radiation such as radio waves, visible lights, Xrays and gamma rays
RADIANT ENERGY
flows of electrons
constitutes an electric current which passes
from negative to positive; In the past it is
usual to trace currents from positive to
negative
ELECTRON THEORY
this theory postulated
that electricity was an invisible &
weightless fluid, present on all objects but
capable of being disturbed
ONE FLUID THEORY
Characteristics of Charged Body
a) Distribution of the Charge
b) Behavior of like & unlike charges
c) Transmission of Electric Charge
Is always held on the surface of
the object; the charge tends to concentrate
where the curvature of the surface is
greatest; it spreads evenly over a sphere but
concentrates at the edges & corners of a flat
plate
-Electric charge
Like charges repel; unlike charges attract
(true or false)
true
An electrically charged object can produce
charge on another object by contact or by
induction.
Transmission of Electric Charge
production
of static electric charge in one object by
another without contact between them.;
ELECTROSTATIC INDUCTION
the area around a
charged body in which the forces resulting
from the charge are apparent; it is most
concentrated close to the charged object,
becoming weaker as the distance from it
increases (forces of attraction or repulsion
ELECTRIC FIELD
the forces
resulting from the charge act along definite
line
ELECTRIC LINES OF FORCE-
straight lines radiating outwards &
perpendicular to the surface
- Sphere
most concentrated at the edges
or points
Irregular Body
LOF
pass from one to another but spread out
somewhat especially at the edges of the field as
they tend to repel each other
Between 2 objects with opposite charges-
LOF concentrate on it
because they can pass through it easily
If with Conductor
properties exhibited
by charged body result from the stored up or
potential, energy of its electric charge & its
electrical conditio
ELECTRICAL POTENTIAL
- an object with excess
electrons
Negative Potential
one with deficiency in
electron
Positive Potential
Unit for potential
volt
The potential varies ______ with the
quantity of electricity with which the object
is charged
directly
quantity of electricity measured; SI unit for electric charge
coulombs
ability of an object to hold an electric
charge & depends on
CAPACITY
Conductors have the greatest power
of storing a chargE
Material
charge is always on the surface of
the object; so the greater the surface area the
greater is the capacitY
Surface area
The potential varies ______ with the
capacity of the object
inversely
Electrical potential varies ______ with the
quantity of charge & inversely with the
capacity of the objecT
DIRECTLY
2 Essential for electric current
production
- Circuit
- Difference of potential
gives rise to a force,
known or EMF; Is maintained and
current continues to flow
Potential difference
frictional force that
opposes the flow of an electric charge;
measured in ohms
Resistance
FACTOR AFFECTING RESISTANCE
- The material of the conductor
- the length of the pathway
- Cross-sectional area of the conductor
- Temperature
resistances are
connected together end to end so that the
current has only one pathway. R= total
resistance
RESISTANCES IN SERIES-
resistances are connected so that
they tap the main circuit at two
points & thus provide alternative
pathways for the currenT
RESISTANCES IN PARALLEL
the relationship between
EMF, resistance & intensity of CurrenT
Ohm’s Law-
The Intensity of an electric current varies
_______ with the EMF & ________ with the
resistance of the conductor
DIRECTLY ; INVERSELY
DEVICES WHICH
REGULATE INTENSITY OF
CURRENTS
- Rheostat
- Variable resistance
- Potential divider
it consist of a coil of wire of
some material offering a fairly high
resistance such as german silver, wound
on a block of insulating material; may be
straight or circular in shapE
- Rheostat
aka series rheostat;
while suitable for regulating current
supplied to certain pieces of apparatus,
such as UVR lamps; this device cannot be
used for regulating the current to a pt
because a pt in the circuit would receive a
shocK
- Variable resistance
this device enables the
current to be regulated from zero, so it is
suitable for controlling the current
supplied to a pt.
Potential divider
production of electric or
magnetic properties in one object by
another without contact between them
- INDUCTION-
is the
production of a static electric charge in
one object by another without contact
between them
ELECTROSTATIC INDUCTION
production
of an electrical properties in one object by magnetic lines of force surrounding another
object without contact between them
ELECTROMAGNETIC INDUCTION
the area around a charged
body in which the forces resulting from the
charge are apparenT
ELECTRIC FIELD
a difference of potential gives rise to a
force known as
EMF
an electric current that
flows in one direction only & is
substantially constant in value
DIRECT CURRENT
an electric
current that reverses direction, according
to a consistent sinusoidal pattern
ALTERNATING CURRENT
states that the amount of
heat produced in a conductor is
proportional to the square of the intensity
of current, the resistance & the time for which the current flows
JOULE’S LAW-
- are
compounds whose molecules consist of the
ions of the constituent elements held
together by the attraction of their opposite
electrical chargeS
ELECTROVALENT COMPOUNDS
elements are
held together by shared electron bonds
COVALENT COMPOUNDS
groups of atoms which are
frequently found in union with each other
RADICALS-
substance which contains more
hydrogen than hydroxyl ions
ACID
SUubstance which contains more
hydroxyl than hydrogen ions
ALKALI-
forces acting
along a definite lines
MAGNETIC LINES OF FORCE
The strength of the induced
EMF is proportional to the rate of change of
the magnetic fielD
FARADAY’S LAW
the direction of the induced EMF
is such that it tends to oppose the force
producinG
- LENZ’S LAW-
circular currents at right
angle to the magnetic lines of force;
undesirable as they tend to reduce the
magnetic effect of the current by setting up a
magnetic field in opposition to the original one
EDDY CURRENTS
a collecting device used to convey the current from the moving coil of
wire to the external circuit; this may
transmit the A.C directly to the circuit or
may change into D.C
DYNAMO-
